Question: On the first 4 tests of his geometry class, Ben got an average score of 78. What does he need on the next test to have an overall average of 82?
Let his score on the next test be $x$ The sum of all of his scores is then $4 \cdot 78 + x$ The same sum must also be equal to $5 \cdot 82$ Solve: $x = 5 \cdot 82 - 4 \cdot 78 = 98$.